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Old 09-01-2005, 05:19 PM   #1
Matt Monson
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Default My engine is NOT the high CR we thought!

Ok,
Advance warning. This post is going to be long as it contains quite a detailed string of events. The short answer is that I am not and have not been running 11.4:1. In fact, I am running very very close to stock! Anyways, here's the story:

I have been talking to I-Speed about the reflash for my car. During that discussion, we started talking about my CR. I told Bill about my head gasket, which he discussed with Quirt Crawford. Now, up until this point, I thought I had a .027cm gasket. More on this later. Bill and Quirt expressed concerns about the non-stock gasket and it's impact on cam timing. Even though we are talking thousandths of thickness off of stock, it was enough of a difference they felt it would be advancing my timing.

This led to some discussion about the gasket itself. According to Quirt, the thinnest gasket Cometic is willing to make for him is .027" .027cm and .027" are far different. I verified that in fact, my gasket is .027"

And here is where it gets interesting. According to Quirt, the stock phase II factory gaskets are .020"=.0508cm. This would mean my CR is actually less than stock! At this point I went back and looked at the CR calculations that Patrick Olsen did in January when "I fragged my motor" (title of the thread for those who want to go back). It appears that he was using .040" as the phase II thickness and that he correctly used .027" regarding my gasket. But he came up with 11:1 and 11.4:1 respectively. There has to be an error there somewhere. I am going to personally run the numbers in the next few days to sort that out.
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Old 09-01-2005, 05:22 PM   #2
Matt Monson
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Part II.
This all left me scratching my head regarding my dyno numbers and my changes in power. I am not going to run through all of that again. If you want the history, check "my dyno results" It has runs both before and after the HG change. The first dyno run with the cams in had me around 205chp. The second run after the HG change had my at 220-225chp. So, I was left wondering how on earth did I pick up 15hp if I actually went to a marginally thicker HG? Was it the timing change that Quirt and Bill referred to? The answer is "no". Thankfully I am a pack rat.

Last night I went home and pulled out the HG's from the engine I blew in January. Some of you will recall that those gaskets were part of a warranty HG replacement from July '04, which is when the cams went in the car in the first place. When they did that work, they had to mill the heads a bit because they were warped. Factory tolerance is only .005, so it can't have been very much. What I didn't realize until last night was that they used a phase I .060"=.152cm HG when they put it back together!

Suddenly it all made sense. The 205chp when I was running it at Cobb had always seemed low to me. For a while I was even suspicous that they had switched my cams to mild instead of spicy because they don't like to sell those cams without headwork. But that was not the case. The case is I was running a CR somewhere down in the 9's!!! So, of course when I install the .027" gasket my HP goes up!

Now where does this leave us? Personally, if I were building an Ej25 today, I would use the stock gaskets. With my milled heads and the .027" gasket I am probably pretty damned close to STOCK CR on my engine. And my power levels are still what they always have been. But all this talk I've been making the last few months about the benefit of the .027 Cometic HG are a load of hoey. Do what you will with this information...

Last edited by Matt Monson; 09-01-2005 at 05:48 PM.
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Old 09-01-2005, 05:57 PM   #3
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Hmmmm. Interesting. Guess I need pistons and rods anyway. I'm going to the dyno saturday to test the full E85 tune. I'll let you know how it goes .
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Old 09-01-2005, 09:39 PM   #4
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thank you, thank you, thank you, sorry to hear about your mistake but it happens to the best of us. OEM is the way to go!!!!
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Old 09-01-2005, 10:00 PM   #5
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The difference between the thicker gasket and the thinner gasket picks up about 15-20 hp per the dyno-run, which is a significant gain for NA cars
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Old 09-01-2005, 10:33 PM   #6
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I was always a bit bewildered by the constant use of .027cm measurements in previous threads. The gaskets I get have always been .027". I will say that the SOA gaskets use a middle layer of compressable material (aluminum) where the Cometic uses full stainless construction. Pricing puts both very close and for me would come down to an availability issue.

It sucks that the misinformation on this forum has led to years of blindly accepting the numbers for empirical truth. Glad we are at the bottom of this now.

Maybe I can get Cometic to make some "true" thin gaskets? Can we pop the locating rivets off and remove the middle layer? I don't see whythehellnot......


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Old 09-01-2005, 11:16 PM   #7
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I guess you were not able to measure the CC's of the differant parts of the motor?
That's your imperical truth.Static wise anyway.
There's been plenty of wrong info on here for sure.Some people will buy pistons from wherever to raise or lower their CR and be for sure what the CR is because that's what they were told.
Did they CC out the cylinders,combustion chambers of the heads...
Ahh nevermind.I"ll shut up on that.
Glad you got it somewhat figured out.
I have a spreadsheet around this computer somewhere.One you can actually calculate with if you know all your measurements.As in thickness of gasket and bore will give you surface area yada yada yada.
Not doggin anyone.Just feeling their pain.

Tod
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Old 09-01-2005, 11:30 PM   #8
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yeah, i figured as much, but didn't want to make a stink, because when i installed my 'low profile' cometic gaskets they were the exact same size as the old ones i pulled out (as far as i could tell at least)
oh well....
chalk it up to....i dunno
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Old 09-02-2005, 12:26 AM   #9
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I offered some input in the "This should be the last EJ-22T thead" on certain setups when they asked,BUT the disclaimer was you don't know unless you CC everything out.
For example:How many CC's are in your cylinder at TDC without the heads on.
My EJ-22T motor was .010" over deck.Still have too figure piston volume.

How many CC's in your combustion chamber with heads on at TDC.
Can only do that after you assemble motor if you use oil too measure.Gotta get the math out if you don't.

I'm getting OT on Matt's thread I guess but I don't post much and this is one subject that is important to me.That and what I'm posting doesn't really have much to do with his situation.

Have to find that calculating spreadsheet.I'm afraid it's on my work computer and I'm not employed there anymore.Not sure if the person I got it from would mind it getting around.
Cough,Techworkseng,cough.

Tod
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Old 09-02-2005, 10:59 AM   #10
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Default Excellent data...

Well, this leaves us with 2 options:

1- The STI gasket is thinner than stock. I can't remember the number, but its the thinnest you can get, as I recall.

2- You could always O-Ring the block. Phase 2 pistons do not clear the deck, correct? That might be good for a huge gain in compression.
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Old 09-02-2005, 11:12 AM   #11
Matt Monson
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Quote:
Originally Posted by staticfritz
yeah, i figured as much, but didn't want to make a stink, because when i installed my 'low profile' cometic gaskets they were the exact same size as the old ones i pulled out (as far as i could tell at least)
oh well....
chalk it up to....i dunno
In the future, question, question, question. Anyone who knows me well knows my old signature," I don't care who's right are wrong, I just want to know the right answer!"

Storm,
I am sure that you clearly told me .027" from the beginning. But you know how the internet is, once it gets said once, it multiplies like a freaking mouse colony. This is just a reminder to not take the word of us old timers as gospel. While we may know a lot about these cars, we are not infallable. I repeat, question everything!

todnar,
Your comments are very relevant. If one is serious about building an engine that goes beyond the mid 11's in CR, or is going to see a ton of boost, you absolutely want to measure everything. Here in our shop, we cc and match the cylinder heads on all of our customers' race builds. It' part of the blueprinting process. If one is serious about building a performance engine, you've got to do that.

There is a big difference between our street driven toy cars and a racecar. We can play around with bits and pieces to a certain extent, but there is a line there. That is why you see such a spike in cost to do this beyond a certain point. You will pay thousands of dollars for that last 15-25hp.

Eventually, I will suck it up and play in that game. My Ej257 block with high CR pistons is coming close to a reality. But my pursuit the last year or so was to see how far you can take it without going there. I don't believe (and have shown) that you don't need $2500 heads to get to stock WRX power levels. You also don't need to replace your pistons. Right now, I am interested to see how much more power the I-Speed reflash is going to yield me. And of course, I will keep you all in the loop as that happens...

One final note. This has shown me yet another mistake on the Ej calcs site that many of us have referenced when we run calculations. It says the phase II HG are .058cm. They are not. They are .0508cm=.020"
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Old 09-02-2005, 11:27 AM   #12
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Quote:
Originally Posted by Matt Monson
Ok,
Advance warning. This post is going to be long as it contains quite a detailed string of events. The short answer is that I am not and have not been running 11.4:1. In fact, I am running very very close to stock! Anyways, here's the story:

I have been talking to I-Speed about the reflash for my car. During that discussion, we started talking about my CR. I told Bill about my head gasket, which he discussed with Quirt Crawford. Now, up until this point, I thought I had a .027cm gasket. More on this later. Bill and Quirt expressed concerns about the non-stock gasket and it's impact on cam timing. Even though we are talking thousandths of thickness off of stock, it was enough of a difference they felt it would be advancing my timing.

This led to some discussion about the gasket itself. According to Quirt, the thinnest gasket Cometic is willing to make for him is .027" .027cm and .027" are far different. I verified that in fact, my gasket is .027"

And here is where it gets interesting. According to Quirt, the stock phase II factory gaskets are .020"=.0508cm. This would mean my CR is actually less than stock! At this point I went back and looked at the CR calculations that Patrick Olsen did in January when "I fragged my motor" (title of the thread for those who want to go back). It appears that he was using .040" as the phase II thickness and that he correctly used .027" regarding my gasket. But he came up with 11:1 and 11.4:1 respectively. There has to be an error there somewhere. I am going to personally run the numbers in the next few days to sort that out.
I am glad that we could help you out with this issue. If you have any more questions please ask, as we are here to help / return to the Subaru comunity that puts food in our mouths.

www.crawfordperformance.com
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Old 09-02-2005, 11:34 AM   #13
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For your calculations use 1.5mm for the phase one gasket and .5mm for the phase two gasket. The .020" number I gave Bill was rounded up for clarity.

www.crawfordperformance.com
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Old 09-02-2005, 11:48 AM   #14
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Quote:
Originally Posted by ballitch
thank you, thank you, thank you, sorry to hear about your mistake but it happens to the best of us.
What he said. Maybe this will further the search for power from the N/A.. Thanks.
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Old 09-02-2005, 11:57 AM   #15
Matt Monson
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Thanks Quirt,
I meant to thank both you and Bill in my first post...
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Old 09-02-2005, 04:34 PM   #16
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Hmm, I did the math not long ago and came up with 11.2 CR without milling the heads, I guess I made the same mistake. That's actually kind of a relief, I was a little worried about running 11+ CR and nitrous on my daily driver. But I don't want less than 10.0 CR, are you sure milling the heads is enough to get back to stock?
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Old 09-02-2005, 04:38 PM   #17
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Quote:
Originally Posted by Storm
Can we pop the locating rivets off and remove the middle layer? I don't see whythehellnot......


Jay Storm
I still have the Cometics I bought from you, I just got my heads off yesterday so I'm ready to install. I'd be willing to be the guinea pig for this is I can be sure I can do this without messing the gasket up. Will the gasket still work properly without the middle layer? Would it be hard to remove the rivets without damaging the gasket? Can I reuse the same rivets when putting it back on?

I think I'm gonna go get one of the gaskets out of the garage and take a look...
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Old 09-02-2005, 05:52 PM   #18
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Quote:
Originally Posted by jasona
Hmm, I did the math not long ago and came up with 11.2 CR without milling the heads, I guess I made the same mistake. That's actually kind of a relief, I was a little worried about running 11+ CR and nitrous on my daily driver. But I don't want less than 10.0 CR, are you sure milling the heads is enough to get back to stock?
It all depends on how much you mill off. But technically, no you cannot mill enough and stay within spec to get to stock. But I think you missed the underlying point. My power level is what it is. The difference between my head that was probably milled .001 or .002 and yours will be a very minor difference in compression. If you continue with your build unaltered, you can expect to be very close, if not the same power that I have. Nothing has changed there. I am still making around 220Chp...
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Old 09-02-2005, 10:39 PM   #19
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Quote:
Originally Posted by jasona
I still have the Cometics I bought from you, I just got my heads off yesterday so I'm ready to install. I'd be willing to be the guinea pig for this is I can be sure I can do this without messing the gasket up. Will the gasket still work properly without the middle layer? Would it be hard to remove the rivets without damaging the gasket? Can I reuse the same rivets when putting it back on?

I think I'm gonna go get one of the gaskets out of the garage and take a look...
You can give it a try, but I would rate the chances of it working at 10%
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Old 09-02-2005, 10:40 PM   #20
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Quote:
Originally Posted by Matt Monson
Thanks Quirt,
I meant to thank both you and Bill in my first post...
You are quite welcome

Quirt
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Old 09-02-2005, 11:41 PM   #21
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Quote:
Originally Posted by Crawford Performance
You can give it a try, but I would rate the chances of it working at 10%
Why is that? Gasket won't seal without the middle layer? When I looked at it I noticed the middle layer is silver while the top and bottom are black, different material?

Maybe I'll just leave well enough alone then. I guess I can settle for ~220 hp + a 50 shot
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Old 09-03-2005, 01:19 AM   #22
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Damnit.

Thanks for the update - and just in time, too, since I was going to switch mine out tomorrow.

I guess maybe I can return them...
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Old 09-03-2005, 03:27 AM   #23
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Interesting to say the least.
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Old 09-03-2005, 05:30 AM   #24
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I'm not technical at all but from the information I have consumed over the last 9 months I don't think it's worth messing with the head gasket.

General consensus for NA motors is to upgrade the cams, headers, exhaust and possibly the intake. Other than that it's about dumping large amounts of money into a futile cause.

I will add that it sounds like the PerfectPower ECU may be sweet addition.
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Old 09-05-2005, 02:34 AM   #25
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Well, I'm really glad that I never sprang for a set of Cometics. Digging up the cash for the Delta Cams was pretty easy, the HG's were another story. Anyways, with just the cams, I'm at 180 CHP, off the 1.8 ecu
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